If the price elasticity of demand is 5, and prices increase by 10%, calculate the percentage change in quantity demanded. Explain which TOF smartphones and Apple iPhones would be considered substitutes or complementary goods in terms of changes in price, and what impact a change in quantity would have. Is the cross-price elasticity of demand positive or negative, and why? Explain which TOF smartphones and phone chargers would be an example of substitutes or complementary goods.